The latest upgrades boost the Ram's towing capabilities, allowing it to tow a maximum 22,700 lbs 5th wheel and 12,000 lbs conventional. Additionally, the gross combined weight rating is now a maximum 30,000 lbs, increased from a previous 24,500 lbs. Despite the increased performance, the 6.7L Cummins does not require the use of diesel exhaust fluid (DEF) and Dodge maintains the standard 5 year/100,000 mile warranty. The Ram has officially stepped back into the game, surpassing GM's Duramax in torque and matching Ford's Power Stroke, though the 6.7L Power Stroke and 6.6L Duramax still have the Cummins beat in horsepower.
Both the current Duramax and Power Stroke require the use of diesel exhaust fluid. While it may be an inconvenience to keep the DEF tank filled, use of selective catalytic reduction has allowed the Duramax and Power Stroke to achieve greater fuel economy potentials than the non-SCR 6.7L Cummins.
Curious as to how the engine receives such a big boost in torque without touching the horsepower? It's explained by the fundamental difference between horsepower and torque. In simplified terms, torque is a measure of twisting force and is completely independent of time. Horsepower, however, is a measure of engine power with relationship to time (and thus engine speed). On a diesel engine, peak horsepower is always near the top of the usable rpm range, while torque is closer to the bottom. For the 6.7L Cummins, peak torque is achieved at 1,600 rpm, while peak horsepower is at 3,000 rpm.
In reality, the new high output 6.7L Cummins receives increases in both torque & horsepower. At 1,600 rpm, the engine is making approximately 20% more horsepower than the previous model. So how is peak horsepower not affected? Simple, towards the end of the usable rpm range (approaching 3,000 rpm), their is no increase (or a negligible increase) in torque over the previous variation of the engine. This means the peak horsepower is unaffected, while the peak torque increases by 150 lb-ft. The higher end of the rpm range does not receive a considerable torque increase.
Source: Ram Trucks, ramtrucks.com